Brainstorming with other founders

Talking to other startup founders, I often brainstorm similar businesses to theirs. Very often though I encounter a psychological wall: “That’s not what we do. That’s not what I’m working on. I don’t care about that angle of the problem or that customer”. I understand it could be taken as criticism and the founder really wants to focus on shipping the thing in his mind. But I also think it’s a missed opportunity. I’m happy for people to brainstorm ideas tangential to my business even if I have no intention of doing them for now: 
  • They may be good ideas for competitors who are doing things just a little too similar to mine.
  • Listening to others' ideas is a good way to start any relationship.
  • They may good ideas for me in 6 months’ time once I’ve nailed/failed a market. 
  • They may complementary product offerings I could seek a partnership with.
  • Merely understanding what’s possible in the space establishes credibility for you with customers and investors. 
  • The context may help me understand the greater value of the business to a broader market, rather than the one idea I’m clinging to. 
  • Elements of the idea may be more viable than I first think.